What are basic indications when this happens.. is the head gasket to be replaced

As necessary, machine head, repair valves, and replace head gasket.

what are basic indications when this happens.. is the head gasket to be replaced

Classic symptoms of a failed head gasket. Do as Txgreasemonkey has suggested but also now is the time to consider replacing the timing belt and resealing the front of the engine. Also, if you haven't done so, consider replacing the water pump and thermostat. These things are often overlooked while replacing the cylinder head gasket, but should be considered since you're going to have far better access to them while the head is off.